Management of power states in a portable computing device

ABSTRACT

Embodiments of the present invention provide a method and apparatus for managing power states in a personal computing device, while maintaining a perception by the user of “instant on” functionality. In various embodiments of the invention, the power states are presented to the user as a simple on/off option and the power management protocol is not visible within the user interface of the personal computing device thereby providing the user with the impression that the system is operating with a simple binary on/off protocol. In one embodiment of the invention, the personal computing device is operable to transition between a set of power states that include: 1) an “on” power state wherein the display is on and the customer can use all input devices; 2) a “ready” state wherein the display is turned off, but some modules, such as a radio module, remain on; 3) an “off” state wherein the personal computing device turns off after a slight pause, but a “booted kernel” is held in SDRAM; and 4) a “dead” state wherein none of the modules of the personal computing device are powered and the device must be cold booted to restart.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Embodiments of the present invention relate in general to the field ofportable computing devices and, more particularly, to an improved methodand apparatus for the management of power states in a portable computingsystem.

2. Description of the Related Art

In recent years, there has been a rapid expansion of the use of personalcomputing devices, particularly those adapted for portable use. Personalcomputing devices include lightweight portable computers, such ashandheld computers, “palmtops,” and personal digital assistants (PDAs),that typically weigh one to three pounds. These personal computingdevices generally provide some combination of personal informationmanagement, database functions, word processing, and spreadsheets aswell as voice memo recording, wireless e-mail, and wireless telephonyfunctions.

Since personal computing devices are generally battery powered, it isimportant to maximize battery life to enhance the usability of suchdevices. It is also desirable, however, to provide users with rapidaccess to software applications. Some personal computing devices, suchas PDAs, provide “instant on” functionality, but do so by draining thebattery during the “off” state. It is possible to simulate “instant on”in laptop computers; however, it is still necessary to drain batterypower in the “off” state. Prolonged periods of inactivity result in theneed to shut the computer off completely, thereby requiring execution ofa full or abbreviated reboot procedure.

As will be understood by those of skill in the art, it is highlydesirable to minimize the time needed to place the device in a fullyoperational state. At the same time, however, it is important tominimize the amount of battery power needed to maintain the device in astate that gives the user the perception that the device is instantlyactivated. In view of the foregoing, there is a need for a method andapparatus that is capable of providing effective power management for apersonal computing device, while minimizing the latency experienced byusers.

SUMMARY OF THE INVENTION

Embodiments of the present invention overcome the shortcomings of theprior art by providing a method and apparatus for managing power statesin a personal computing device, while maintaining a perception by theuser of “instant on” functionality. In the method and apparatus ofembodiments of the present invention, power states are presented to theuser as a simple on/off option. The implementation of the powermanagement protocol is not visible within the user interface of thepersonal computing device and provides the user with the impression thatthe system is operating with a simple binary on/off protocol.

In one embodiment of the invention, the personal computing device isoperable to transition between a set of power states that include: 1) an“on” power state wherein the display is on and the customer can use allinput devices; 2) a “ready” state wherein the display is turned off, butsome system modules, such as a radio module, remain on; 3) an “off”state wherein the personal computing device turns off after a slightpause, but a “booted kernel” is held in SDRAM; and 4) a “dead” statewherein none of the modules of the personal computing device are poweredand the device must be cold booted to restart.

When the personal computing device is in the “ready state,” it drawssome power to maintain “readiness,” but is capable of turning oninstantly. When the personal computing device enters the “off” state,the operating system kernel remains stored in memory. In this state, allsystem peripherals are shut down, but the contents of the system memory(including the operating system kernel) remain intact. In this state,the only power draw from the battery is to maintain the contents of theRAM and the system clock, allowing the personal computing system to cometo life quickly. When the personal computing device is in the “dead”state, it must be “cold booted” to resume normal functionality, i.e.,the system clock will need to be reset and, in some cases, it may needto be charged for a period of time before the device can be restarted.

As will be understood by those of skill in the art, the method andapparatus of embodiments of the present invention is capable ofproviding effective power management for a personal computing device,while minimizing the latency experienced by users.

BRIEF DESCRIPTION OF THE DRAWINGS

The embodiments of the present invention may be better understood, andits numerous objects, features and advantages made apparent to thoseskilled in the art by referencing the accompanying drawings ofembodiments of the invention. The use of the same reference numberthroughout the several figures designates a like or similar element.

FIG. 1 is a generalized illustration of a computing system, such as aPDA, that can be used to implement the method and apparatus of anembodiment of the present invention.

FIG. 2 is a logic diagram illustrating operation of the power managementsystem according to an embodiment of the present invention.

FIG. 3 is a state diagram illustrating operation of the power managementsystem according to an embodiment of the present invention.

DETAILED DESCRIPTION

FIG. 1 is an illustration of major functional components used in apersonal computing device 100 or PDA used to implement the method andapparatus of an embodiment of the present invention. Personal computingdevice 100 includes a processor 110 which may be any of a variety ofconventional processing devices. A memory 120 is coupled to processor110. Memory 120 may be any of a variety of volatile and non-volatilememory devices including, but not limited to, read only memory (ROM),random access memory (RAM), flash memory, etc. Memory 120 may beutilized to store programs running on processor 110, and/or may be usedto store other types of information. An input/output (I/O) module 130,which includes a wireless radio interface is coupled to processor 110 toprovide for transport of data and control signals into and out of thepersonal computing device 100. Personal computing device 100 alsoincludes a display 140. Display 140 may be any of a variety of displaysincluding, but not limited to, an LCD touch screen display. Display 140may be used to display information to a user of personal computingdevice 100. Other data processing functional modules, illustratedgenerally by reference number 150, can provide a plurality of dataprocessing functions, such as memory management, graphics processing,and other functions known to those of skill in the art. A powermanagement module 160 is operable to control the power consumption ofthe various functional modules of the personal computing device 100, asdiscussed in greater detail hereinbelow. As will be understood by thoseof skill in the art, the processor 110 and the other functionalcomponents 150 in the personal computing device 100 can be connectedusing one or more buses illustrated generally by bus 170 in FIG. 1.

Embodiments of the present invention overcome the previously mentionedshortcomings of the prior art by providing a method and apparatus formanaging power states of the personal computing device 100, whilemaintaining an “instant on” functionality. In an embodiment of thepresent invention, the personal computing device 100 transitions from an“on” state to a plurality of reduced power states after a predeterminedperiod of inactivity. In another embodiment of the invention, thetransition from the “on” state to a plurality of reduced power states ispresented to the user as a simple “on/off” option.

The power management module implements a power management protocol thatis not visible from the user interface. While the user may notice aslight difference in turn-on time associated with the transition fromsome power states to the “on” state, the overall operation of the systemprovides the user with the impression that the system is operating witha simple binary “on/off” protocol.

FIG. 2 is a logic diagram illustrating an embodiment of the powermanagement functionality implemented by the power management module 160.The personal computing device is initially powered-up from a cold bootas designated by the “start” state 200. After the initial power up, thepower management module 160 provides four power possible states: 1) an“on” power state (designated by reference numeral 202) wherein thedisplay is on and the customer can use all input devices; 2) a “ready”state (designated by reference numeral 204) wherein the display isturned off, but some modules, such as a radio module, remain on; 3) an“off” state (designated by reference numeral 206) wherein the deviceturns off after a slight pause, but a “booted kernel” is held in SDRAM;and 4) a “dead” state (designated by reference numeral 208) wherein noneof the modules of the device are powered and the device must be coldbooted to restart.

The state of the applications and system modules for each of theaforementioned operating states is summarized briefly in the transitionblocks illustrated in FIG. 2. The “on” state 202 is the normal operatingstate wherein the user is actively using the personal computing device100. After a predetermined period of inactivity, the power managementmodule causes the personal computing device to migrate to the “ready”state 204. When the device is in the “ready” state, it draws some powerto maintain “readiness,” but is capable of turning on instantly. Whenthe device is in the “off” state 206, all applications are shut downfirst and only the operating system kernel remains in the RAM. Each ofthe applications saves its state information to non-volatile storage.The operating system then saves the system state with no runningapplications. In this state, all that remains in RAM is enough code forthe system to be able to come back to life quickly. Power drain islimited to an amount needed to maintain the system clock and to keep theRAM powered. When the system is in the “dead” state 208, the system willneed to be returned to the “start” state 200 by the user for a coldboot, the system clock will need to be reset and, in some cases, thesystem may need to be charged for a period of time before the system canbe restarted.

The transition of the personal computing device between the variouspower states is illustrated in the state diagram of FIG. 3. Thetransition from one state to another state can be based on a detectionof a predetermined period of inactivity or on a specified user input.The personal computing device 100 executes first, second, and thirdtimers that are used to measure time intervals for initiating thetransition from one power state to another power state. The personalcomputing device 100 can transition from any power state to the “on”power state upon detection of I/O activity or upon detection of a userinput. If the personal computing device 100 is operating in a reducedpower state, it can transition to the “on” state if the user presses thepower switch 162.

Referring to FIG. 3, the personal computing device 100 can transitionfrom the “on” state 202 to the “ready” state 204 either as a result of auser input or as a result of inactivity for a predetermined period oftime. In an embodiment of the present invention, the display 140 of thepersonal computing device 100 turns off immediately when the userpresses the power switch 162 or closes the screen to power-down thesystem. In this embodiment, the first timer will be truncated and thesystem will immediately enter the “ready” state 204. The personalcomputing device will also automatically transition from the “on” state202 to the “ready” state 204 if it receives no input from the userconfigurable amount of time, e.g., ten minutes. Any state savingactivity continues while the video screen is off. The personal computingdevice can be returned to the “on” state 202 upon detection of I/Oactivity or if the user presses and releases the power switch 162. In anembodiment of the present invention, the video display is illuminated inan extremely short time period, e.g. 100 ms, when transitioning from the“ready” state 204 to the “on” state 202 to give the illusion of instantturn-on. Since the various user-selected applications are maintained inan “active” state, the transition from the “ready” state 204 to the “on”state 206 does not adversely affect any of the applications running onthe system.

If the personal computing device 100 is not returned to the “on” state202 within a predetermined period of time, e.g., 30 minutes, the systemtransitions from the “ready” state 204 to the “off” state 206. Asdiscussed above, this state allows the system to keep power drain as lowas possible, while still keeping the operating system kernel booted. Inan embodiment of the present invention, using a battery 164 having arating of 6800 mAh, the system is capable of staying in the “off” mode206 for up to four months. Upon detection of I/O activity or upon userinput, such as pressing the power switch 162, the system is capable ofreturning to the “on” state 202 in a very short period of time, i.e.,500 ms, and the combination of the operating system kernel in RAM andthe operating state saved to non-volatile memory are used to return thesystem to the previous state.

If the system is not returned to the “on” state for a very long periodof time, i.e. several months, the low level power draw in the “off”state will eventually cause the system to transition to the “dead” state208. From the “dead” state 208, the system proceeds through the coldboot cycle, just like the first time it was booted at the “start” state200.

As will be appreciated by those of skill in the art, the method andapparatus of an embodiment of the present invention is capable ofproviding effective power management for a personal computing device,while minimizing the latency experienced by users. Although embodimentsof the present invention have been described in detail, it should beunderstood that various changes, substitutions and alterations can bemade hereto without departing from the spirit and scope of the inventionas defined by the appended claims.

1. A personal computing device, comprising a display; a plurality ofdata processing modules; a volatile storage; a non-volatile storagehaving an operating system and a plurality of software files storedthereon; and a processor to use said operating system to executeselected software files in said plurality of software files and toimplement a power management function to transition the powerconsumption of said display and said plurality of data processingmodules to first, second and third reduced power states based upon a setof predetermined operating parameters and to return the personalcomputing device to a full active state upon detection of input/outputactivity, wherein the display is illuminated prior to completing thetransition from any of the first, second or third reduced power statesto the full active state in order to simulate instant on functionalityfor the personal computing device.
 2. The personal computing deviceaccording to claim 1, wherein said processor executes first, second andthird timers corresponding to said first, second and third reduced powerstates and wherein said processor is further to transition the powerconsumption of said display and said data processing modules to saidfirst, second and third reduced power states upon expiration of saidfirst, second, and third timers, respectively.
 3. The personal computingdevice according to claim 2, wherein said first timer is truncated by auser input, thereby placing said personal computing device in said firstreduced power state.
 4. The personal computing device according to claim3, wherein said display is placed in an inactive state and said volatilestorage is maintained in an active state.
 5. The personal computingdevice according to claim 4, wherein a plurality of executed softwarefiles are stored in said volatile memory and are maintained in an activestate.
 6. The personal computing device according to claim 5, whereinupon transition to said second power state, said data processing modulesare inactive, said volatile memory is active and wherein applicationstate information and operating system kernel are stored in saidvolatile memory.
 7. The personal computing device according to claim 6,wherein upon transition to said third reduced power state, said dataprocessing modules are inactive and said volatile memory is in aninactive state.
 8. A method of managing power in a personal computingdevice having a processor, a display, a plurality of data processingmodules, a volatile storage and a non-volatile storage with an operatingsystem and a plurality of software files stored thereon, the methodcomprising: using said processor and said operating system to executeselected software files in said plurality of software files to implementa power management function to transition the power consumption of adisplay and said data processing modules to first, second and thirdreduced power states based upon a set of predetermined operatingparameters and to return the personal computing device to a full activestate upon detection of input/output activity, wherein the display isilluminated prior to completing the transition from any of the first,second or third reduced power states to the full active state in orderto simulate instant on functionality for the personal computing device.9. The method according to claim 8, wherein said processors executesfirst, second and third timers corresponding to said first, second andthird reduced power states and wherein said processor is further totransition the power consumption of said display and said dataprocessing modules to a said first, second and third reduced powerstates upon expiration of said first, second, and third timers,respectively.
 10. The method according to claim 9, wherein said firsttimer is truncated by a user input, thereby placing said personalcomputing device in said first reduced power state.
 11. The methodaccording to claim 10, wherein said display is placed in an inactivestate and said volatile storage is maintained in an active state. 12.The method according to claim 11, wherein a plurality of executedsoftware files are stored in a said volatile memory and are maintainedin an active state.
 13. The method according to claim 12, wherein saiddata processing modules are inactive, said volatile memory is active andwherein application state information and an operating system kernel arestored in said volatile memory.
 14. The method according to claim 13,wherein said data processing modules are inactive and said volatilememory is in an inactive state.